LCDs are commonly used flat panel displays currently, and thin-film transistor liquid crystal displays (TFT-LCDs) are the mainstream product among LCDs.
An LCD panel is an important component of an LCD. The production process of an LCD panel is as follows: firstly, an array substrate and a color filter (CF) substrate are produced; and secondly, the CF substrate and the array substrate are assembled by a cell assembly process to form the LCD panel. The cell assembly process may specifically include: dripping liquid crystals on the array substrate or the CF substrate by one drop filling (ODF) process; coating sealant on the other substrate; and subsequently, forming the LCD panel by cell assembling the array substrate and the CF substrate. The uniformity of the cell gap of the formed LCD panel is determined by the uniformity of the post spacers between the CF substrate and the array substrate, and that all the post spacers on the CF substrate and/or the array substrate have relatively uniform height also ensures the product quality under a fixed amount of the liquid crystals. The requirement on the accuracy of the cell gap of the LCD panel is particularly high in the fields of military application, scientific research application and the like having higher requirement on the accuracy. But generally, the height fluctuation of the post spacers between the CF substrate and the array substrate, produced by the patterning process, is unavoidable. Therefore, the adjustment of the post spacers so that the post spacers have uniformity is particularly important.
For the convenience of description, the CF substrate and the array substrate herein are referred to as “substrate” in the following description.
The standard of measuring the uniformity of the post-spacer height (height distribution) is generally that the standard deviation of the post-spacer height is required to be as small as possible. In actual production, if the height uniformity of the produced post spacers is poor, the production of the panel may be adversely affected. The nonuniformity of the post-spacer height on the substrate may be specifically embodied in the fluctuation of the mean value of the post-spacer height among glass substrates and the fluctuation of the heights of various post spacers on panels from one glass substrate.
In the actual production process, the post-spacer height on the substrate obtained after rubbing process has a great impact on the characteristics of the panel, which shows particularly as follows: as the CF substrate and the array substrate obtained after rubbing process are required to be directly subjected to a cell assembly process, poor uniformity of the post-spacer height on the substrates may directly result in the case that the amount of the liquid crystals in the final panel product is not comparable with the post-spacer height, and hence the produced panel may have poor quality. Specifically, as only several post spacers are selected for measurement during the measurement, and it is impossible to reflect the heights of the post spacers on the whole substrate, namely the actual heights of the post spacers on the substrate cannot be reflected. If the measured post-spacer height on the substrate is less than the actual post-spacer height, when a corresponding amount of the liquid crystals are filled according to the measured post-spacer height on the substrate, the phenomena such as low-temperature bubbles will occur; and if the measured post-spacer height on the substrate is more than the actual post-spacer height, when a corresponding amount of the liquid crystals are filled according to the measured post-spacer height on the substrate, the phenomena such as gravity mura will occur. At present, the main solution to this is as follows: the heights of the post spacers on the substrate are extensively measured, and the amount of the filled liquid crystals is accordingly changed. But the solution has certain defect: the amount of the filled liquid crystals is required to be changed along with the fluctuation of the post-spacer height, but the change of the amount of the liquid crystals may result in the change of the cell gap of the panel, and hence the optical property of a final product will be affected.